The watchdog group Safety Research and Strategies brought suit against the National Highway Traffic Safety Administration, which conducted the study of Toyota's vehicles, Monday in U.S. District Court in Washington, D.C., The New York Times reported Wednesday.
The NHTSA concluded the problem, which prompted massive Toyota recalls in 2009 and in 2010, was caused by gas pedals that either became sticky or got caught under floor mats.
The NHTSA did not blame faulty electronic components, which some suspected was the cause of some vehicles suddenly picking up speed.
The watchdog group contends two NHTSA two staff members inspected a Prius owned by Joseph McClelland of Chambersburg, Pa., and documented that the engine repeatedly raced unintentionally. McClelland, meanwhile, has said when the problem surfaced during a 200-mile trip in the car, he placed his toe under the gas pedal only to discover it was up as far as it could go, so it was not stuck. The problem also had nothing to do with a floor mat, he said.
The inspectors filmed the problem during the visit to his home. But when Safety Research requested documents concerning McClelland's vehicle, they were given an incomplete record of the visit to his home, which included no photographs or videos.
McClelland said months after the visit he received a letter that said his car, which had 280,000 miles on it, was too old to allow regulators to draw any concrete conclusions.
"This is all about transparency. This is an agency that selectively releases data that fits its narrative that electronics are not at fault in sudden acceleration," said Sean Kane, co-founder of Safety Research, an auto consulting firm in Massachusetts.
The lawsuit seeks to have all the pertinent NHTSA documents in the case released.